Surveillance footage of an attempted robbery at a Bank of America in Atlanta.

A serial bank robber suspected of murdering a Mississippi police officer and wounding a second one was killed in a shootout with cops in Arizona on Saturday, ending a weeklong manhunt, authorities said Sunday.

Mario Edward Garnett, 40, ran out of a bank with a mask on and a gun in his hand and was shot by a plain clothes officer after he started shooting at agents who were called to the scene, said Phoenix Police Department spokesman James Holmes.

Officials believe Garnett is responsible for similar bank heists in Atlanta and Tupelo, Miss., where he allegedly shot two officers, killing one.

Field officers in Arizona “recognized a method of operations used that was similar to robberies used in other states,” Holmes said.

FBI Special Agent-in-Charge Daniel McMullen said investigators have determined the suspect's cellphone was used in all three cities around the times of the robberies. He said the man wore similar clothing, made similar demands and used a wedge to prop open door to make his escape easier.

AP Photo/Police photo via The Northeast Mississippi Daily Journal

This undated photo provided by the Tupelo, Miss. police shows Sgt. Gale Stauffer, who was killed in the line of duty on Monday Dec. 23, 2013.

The widow of Tupelo Police Department sergeant Gale Stauffer, who was killed while pursuing the bandit after the Dec. 23 stickup, praised law-enforcement.

"Gale would be proud," Beth Stauffer said at a press conference in Tupelo.

"Today is another very emotional day in the life of our family. We can truly begin the healing process," the mother of two added. "We know we have not been going through this alone. Thank you from the bottom of our hearts for shining a light in this time of darkness."

Minutes after the robber stuffed a black bag with cash from tellers' drawers at a BanCorpSouth in Tupelo on Monday afternoon, Stauffer and his partner, Officer Joseph Maher, raced to the scene and stopped a car on the road.

The suspect was in the vehicle behind, jumped out and ambushed the officers, police said. Stauffer was killed and Maher was seriously hurt.

Agents soon linked the cop-killer to an attempted robbery that happened earlier that same day in Atlanta, where the suspect did not get any money from the teller but did rob a customer at a cash machine.

As a $200,000 reward was posted, dozens of tips began to pour in, but the man was still able strike again before the FBI tracked him down.

Officials say a man wanted in connection with multiple bank robberies and the death of police officer Gale Stauffer was killed by police in Phoenix, Ariz.

On Saturday morning, he tried to stick up a Compass Bank in Phoenix, some 1,500 miles from Mississippi, authorities said.

Holmes commended the plain clothes officer who happened to be nearby working a different case for doing “exactly what he should have done.”

Court records indicate that Garnett was sentenced to federal prison for threatening President Barack Obama in notes posted to the White House website in late August 2010.

“If you order a strike on Iran, I’m going to come up there and blow your brains out on national TV,” Garnett’s message intended for the president read. The same note threatened Benjamin Netanyahu, the prime minister of Israel, with equally graphic language.

Garnett was released from prison in July of this year, according to the Federal Bureau of Prisons. He was not allowed to own a gun, according to court documents.

Holmes said Garnett was “a service member” at some point.” Although officials have no record of Garnett living in Arizona, the suspect was from the Midwest, Holmes said.

Tupelo Police Chief Bart Aguirre said the city was devastated by the murder of Stauffer, 28, who was buried Friday.

"This closure has helped us mend and begin to heal that deep, deep wound," he said.